Add SendEmptyRequest Method for shutdown request (#233)

Author: luxxia702

src/Client/LanguageClient.cs

@@ -300,7 +300,7 @@ public async Task Shutdown()
             {
                 if (connection.IsOpen)
                 {
-                    connection.SendEmptyNotification("shutdown");
+                    await connection.SendEmptyRequest("shutdown");
                     connection.SendEmptyNotification("exit");
                     connection.Disconnect(flushOutgoing: true);
                 }

src/Client/Protocol/LspConnection.cs

@@ -352,6 +352,17 @@ public void SendNotification(string method, object notification)
             });
         }
 
+        /// <summary>
+        ///     Send an empty request to the language server.
+        /// </summary>
+        /// <param name="method">
+        ///     The request method name.
+        /// </param>
+        public Task SendEmptyRequest(string method)
+        {
+            return SendRequest(method, EmptyRequest.Instance);
+        }
+
         /// <summary>
         ///     Send a request to the language server.
         /// </summary>